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Darwin, Evolution, and Natural Selection

Darwin, Evolution, and Natural Selection. Lamark Proposed First Hypothesis. Thought giraffes had long necks because they stretched them to reach leaves. Was proven to be wrong . Steps of natural selection. Gene variation among individuals of a population

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Darwin, Evolution, and Natural Selection

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  1. Darwin, Evolution, and Natural Selection

  2. Lamark Proposed First Hypothesis • Thought giraffes had long necks because they stretched them to reach leaves. • Was proven to be wrong

  3. Steps of natural selection • Gene variation among individuals of a population • Variation is often passed on to offspring (offspring look like their parents)

  4. Steps of natural selection • All populations over produce young- only some will survive and reproduce • Likehood an individual will survive and reproduce is not random

  5. Steps of natural selection • Individuals with traits that aid in survival or reproduction with have a better chance at passing traits on to next generation • Over time the traits seen in a population will have those that help individuals survive

  6. Why Lamark Was Wrong • DNA is passed to offspring, not acquired traits.

  7. Charles Darwin • Came up with the idea that evolution happens through natural selection. • Is credited with being the father of evolution

  8. Darwin’s Journey • Accompanied the captain of the H.M.S. Beagle on a journey around the world. • Visited and observed many plants and animals. • Observed some very interesting animals in the Galapagos Islands that helped him discover the process of natural selection.

  9. Map of Darwin’s Journey

  10. Darwin’s Discovery • Noticed that animals seemed to be specially adapted to the places that they lived. • He especially noticed this in a type of bird, called a finch, that lived in the Galapagos Islands. • All of their beaks were specifically suited to the type of food that they ate.

  11. Darwin’s Picture of the Finch Beaks

  12. We have now identified 14 species

  13. Why the different beaks? • Darwin determined that the finches that had the beaks that got the most food lived longer and reproduced more than the ones that didn’t get as much food. • That led him to his idea of natural selection

  14. Natural selection is… • Natural selection says that the organisms best suited to the environment will live to reproduce while other organisms that are not as well suited will die. • This is also known as survival of the fittest (usually misused when you hear it).

  15. Darwin Thought.. • That the finches had adapted to being on each of the islands because each island had different food • Eventually these finches lived apart from each other for so long and changed so much that they could no longer breed with each other. That is what makes a new species.

  16. Darwin’s Picture of how he thought the finches were related

  17. When he got home… • Married his cousin • Was afraid to publish his findings, thought people would be upset with him. • Studied more of his idea by watching pigeons. • Finally published his book On the Origin of Species in 1858 because another scientist (Alfred Wallace) was going to beat him to it.

  18. Darwin’s idea had two parts: • 1. Descent with modification- animals and plants on the earth today are just changed versions of what was here long ago (new animals don’t just come to life out of nowhere).

  19. Darwin’s Idea had two parts: • 2. Modification by natural selection- states how the evolution occurs. Basically those who are most suited to the environment pass on their DNA, those that die…don’t.

  20. Natural selection at work… THEN…

  21. THEN…

  22. Evolution

  23. Fossil Record Embryos Structures Homologous Analogous Vestigial 4. Geological 5.Cellular Evidence 6.Experiments/ Artificial selection 7. DNA Evidence for Evolution

  24. Fossil Record

  25. Fossil Record

  26. Fossil Record Above left, the Cretaceous snake Pachyrhachisproblematicus clearly had small hindlimbs. The drawing at right shows a reconstruction of the pelvis and hindlimb of Pachyrhachis

  27. Embryos

  28. Geological Evidence • Law of superposition • Dating of rocks

  29. Geological Evidence

  30. Cellular Evidence

  31. Experiments/Artificial Selection

  32. DNA

  33. Homologous Structures- Structures that are similar due to common ancestry.

  34. Homologous Structures

  35. Vestigial Structures- Structures that used to function, but no longer have a purpose. • Tailbones in People • Appendix in People • Ear muscles that no longer function in people • Hip bones in Snakes

  36. Analogous Structures- Structures that developed due to environment • Flies and Birds both have wings • Dolphins and Sharks look similar because they live in the same place. • Shows that animals in same habitat tend to develop similar features due to natural selection.

  37. Microevolution leads to macroevolution Microevolution Macroevolution Evolution on a grand scale, way in which new species are formed from old species How did we get all the different species? Changes in the kinds of plants and animals on earth as new forms replace old ones Changes that take place over a long period of time • How a population of species change • Change in gene frequencies • What traits are being expressed • Adaptations

  38. Microevolution • Adaptation- changes that increase the likelihood of survival and reproduction of particular genetic traits in a populations • Adaptations are a result of microevolution

  39. Rate of evolution • Different kinds of organisms evolve at different rates • Bacteria evolves very quickly due to short lifespan and fast reproductive rates • While lungfish have changed little over the past 150 million years

  40. Rate of evolution • There are two theories for the rate of evolution • Punctuated equilibrium- species formation occurs in burst, separated by long periods of stasis • Gradualism- species formation is constantly occurring by accumulating small differences

  41. Molecular clock • Molecular clock is a model that is used to compare DNA sequences from two different species to estimate how long the species have been evolving since they diverged from a common ancestor • Cladogram- a branching diagram that represents the proposed evolutionary history of a species

  42. Genetic change within populations • Population genetics- study of the properties of genes in populations • Alleles- alternative forms of a gene • Allele frequencies- how often a specific allele is found within a population

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